Rotating construction lasers are well known in the prior art. For example, in U.S. Pat. No. 7,370,427 a construction laser with at least one laser beam defining a plane is described. The construction laser has a laser unit that is tiltable relative to a housing around at least one swiveling axis. The construction laser includes at least one leveling sensor which is sensitive to the swiveling axis for a highly precise orientation to the gravitational field. The device further includes one tilt sensor which is sensitive to the swiveling axis for direct measurement of an inclination angle relative to the gravitational field.
Disadvantageous in this embodiment is that a level sensor and a tilt sensor are needed to perform the tilt measurement with an acceptable degree of accuracy. Furthermore, the laser beam unit periodically needs to return to its level position for recalibrating the tilt sensor.
Likewise, WO 2008/052590 A1 relates to indicating a grade, e. g. in construction applications, using a laser beam. The laser beam is emitted from a laser unit to a desired direction having a grade angle with regard to the level angle. A level sensor is provided for adjusting the level angle and a grade sensor is provided for indicating a grade angle on the basis of the level angle from the level sensor.
This device also requires two sensors to correctly indicate the grade.
According to U.S. Pat. No. 5,485,266, fixed tilt detectors are fixed in planes crossing perpendicularly to each other of a shaft center of a laser projector, and tilting tilt detectors are mounted on a plate which is tiltable with respect to the shaft center of the laser projector. The laser projector is level in such a manner that the fixed tilt detectors indicate horizontal direction. The tilting tilt detectors are aligned with the fixed tilt detectors and indicate a horizontal direction. Thus, a horizontal reference plane is obtained. The tilting tilt detectors are tilted with the fixed tilt detectors as a reference and the laser projector is leveled so that the tilting tilt detectors indicate horizontal direction. Thus, a reference plane tilted at an arbitrary angle is obtained.
This device also requires multiple tilt sensors.
As can be seen from the prior art, two tilt sensors are usually used for measuring the tilt of an axis of rotation of a rotating construction laser with high accuracy. One of these sensors is a level sensor which is of very high precision and very limited range and which is used to calibrate the grade sensor or tilt sensor, which has a broader range, but is less precise.